1. Technical Field
This invention relates to adjustable arc of coverage spray nozzles, and more particularly, to such nozzles which have preset spray ranges, and in which an upstream throttling valve is proportionally mechanically coupled to the arc of coverage adjustment so that a substantially constant precipitation rate can be selected and provided as the arc of coverage is adjusted. The invention also relates to sprinkler systems including a plurality of such nozzles with different spray ranges.
2. Relevant Prior Art
Sprinkler nozzles are known which have an adjustable arc of coverage, e.g., as shown in Hunter U.S. Pat. No. 4,579,285, and in my U.S. Pat. No. 5,588,594.
My U.S. patent application Ser. No. 10/100,259 entitled SPRAY NOZZLE WITH ADJUSTABLE ARC SPRAY ELEVATION ANGLE AND FLOW, filed Mar. 15, 2002 discloses an adjustable range and arc of coverage nozzle having an adjustable arcuate spray slot in which the arc setting mechanism is linked to an upstream throttling valve to proportionally control the flow to the spray slot as the arc of spray coverage is increased or decreased. Although other arc-settable spray nozzles that have adjustable upstream throttling valves are also known, the upstream throttling valve areas of these are not preset at the factory during assembly to provide the correct flow rate for the desired range of coverage while still maintaining the same larger adjustable slot width, and if adjusted, are not designed to provide proportionally increasing area openings as the arc of coverage is increased for substantially uniform precipitation independent of the arc of coverage setting.
The short range adjustable arc nozzles which are now on the market have adjustable arcuate slot orifices that are quite thin e.g., less than 0.030 inch, to reduce the flow rates for the shorter ranges of coverage such as 8 feet. These very thin slots are easily clogged and require fin filters having correspondingly small openings, which themselves are easily clogged.
There is accordingly a need for an improved adjustable arcuate slot nozzle in which an upstream proportional flow rate adjusting valve and an arc of coverage adjustment mechanism are coupled so that a substantially constant pre-settable precipitation rate is obtained for different arcs of coverage when the desired flow rate is less than what the adjustable arcuate slot alone provides. The present invention seeks to address this need, in addition to having the nozzles preset at the factory to provide selected shorter ranges of coverage such as 8, 10, 12, and 15 feet.